This invention relates to wireless devices, and in particular, to determining the location of a wireless device.
The need to accurately determine the position of a wireless device is important for the following three reasons: (1) the Federal Communication Commission Enhance 911 mandate requires all carriers to implement a technology for locating their wireless customers automatically. (2) The accurate position of a wireless telephone can be used to greatly improve wireless handoffs from one base station to another. (3) New applications and services are emerging to provide location dependent content to wireless telephones, wireless personal digital assistants (PDA), and other wireless systems. The prior art has approached the problem of determining the location of wireless devices by utilizing global positioning systems (GPS) and network-based locating methods. GPS methods use signals generated from 24 government satellites orbiting the Earth to determine the position of a mobile unit. Though accurate to a few meters, GPS signals are difficult to receive indoors and in some urban environments. Network-based methods involve triangulating the radio transmission or using RF multi-path finger printing methods to identify the most likely position of the radiating source. The multi-path method offers significant performance advantages over triangulation in urban environments.
Unfortunately, neither GPS nor network-based locating methods work well or at all, inside buildings. This is particularly true of office buildings or manufacturing plants which tend to utilize a great deal of concrete with reinforced steel. In addition, the problems of trying to perform either GPS or network-based locating methods within a multistoried building are compounded by the fact of excessive amount of multi-path emissions that are far greater than that encountered outside. It is well known that the handoffs of wireless telephones within multistoried office buildings from one base station to another base station can be greatly enhanced if the location of the wireless telephone can be accurately determined. However, because of the density of the base stations, the location information for the wireless telephone must be accurate to a few meters if it can be efficiently used in the handoff process.
This invention is directed to solving these and other problems and disadvantages of the prior art. An acoustic gyroscope within a device is utilized to accurately determine the location of the device and the acoustic gyroscope is periodically adjusted using information from external sources.